Heat sink



FIG. 1 is a perspective view of a heat sink showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIGS. 8 and 9 are perspective views showing the heat sink in use.

The broken line environmental showing is for illustrative purpose only and forms no part of the claimed design. 

The ornamental design for a heat sink, as shown and described. 